AbstractMicroplastic particles have become ubiquitous in aquatic environments and can be found in large numbers in riverine, estuarine, and marine settings at the surface of water, in suspension, and as particles deposited at the bed. The transport and settling behavior of small microplastic particles is likely very dependent on interactions with other suspended particles. Here we show from settling tube experiments conducted in the laboratory that fragments and threads of polyvinylchloride microplastic in the size range of 63-125 µm readily flocculated with fine-grained natural sediment under relative particle number concentrations that can be observed in nature in high-turbidity estuarine and coastal environments. The implication of this flocculation is that the microplastic particles are suspended and transported incorporated in aggregates that settle faster than the individual microplastic particles. This is causing a continuous sedimentation of microplastic particles in estuarine and marine settings, resulting in increased microplastic loading for benthic life in these environments.AbstractVesicomyid clams, which inhabit deep-sea hydrothermal vents and hydrocarbon seeps, are nutritionally dependent on symbiotic, chemoautotrophic bacteria that produce organic matter by using hydrogen sulfide. Vesicomyid clams absorb hydrogen sulfide from the foot and transport it in their hemolymph to symbionts in the gill. However, mechanisms to cope with hydrogen sulfide toxicity are not fully understood. Previous studies on vent-specific invertebrates, including bathymodiolin mussels, suggest that hypotaurine, a precursor of taurine, mitigates hydrogen sulfide toxicity by binding it to bisulfide ion, so as to synthesize thiotaurine. In this study, we cloned cDNAs from the vesicomyid clam Phreagena okutanii for the taurine transporter that transports hypotaurine into cells and for cysteine dioxygenase and cysteine-sulfinate decarboxylase, major enzymes involved in hypotaurine synthesis. Results of reverse-transcription polymerase chain reaction indicate that mRNAs of these three genes are most abundant in the foot, followed by the gill. However, hypotaurine and thiotaurine levels, measured by reverse-phase high-performance liquid chromatography, were low in the foot and high in the gill. In addition, thiotaurine was detected in hemolymph cells. Hypotaurine synthesized in the foot may be transported to the gill after binding to bisulfide ion, possibly by hemolymph cells.AbstractChitons have a distinctive armature of eight articulating dorsal shells. In all living species, the shell valves are covered by a dense array of sensory pores called aesthetes; but in some taxa, a subset of these are elaborated into lensed eyes, which are capable of spatial vision. We collected a complete ontogenetic series of the eyed chiton Tonicia lebruni de Rochebrune, 1884 to examine the growth of this visual network and found that it expands continuously as eyes are added at the margin during shell growth. Our dataset ranged from a 2.58-mm juvenile with only 16 eyes to adults of 25-31 mm with up to 557 eyes each. This allowed us to investigate the organization (and potential constraints therein) of these sensory structures and their development. Chiton eyes are constrained to a narrowly defined region of the shell, and data from T. lebruni indicate that they are arranged roughly bilaterally symmetrically. We found deviations from symmetry of up to 10%, similar to irregularity reported in some other animals with multiplied eyes. Distances separating successive eyes indicate that, while shell growth slows during the life of an individual chiton, eyes are generated at regular time intervals. Although we could not identify a specific eye-producing tissue or organ, we propose that the generation of new eyes is controlled by a clock-like mechanism with a stable periodicity. The apparent regularity and organization of the chiton visual system are far greater than previously appreciated. This does not imply the integration of shell eyes to form composite images, but symmetry and regular organization could be equally beneficial to a highly duplicated system by ensuring even and comprehensive sampling of the total field of view. Higher mortality among full-term infants (term infant deaths) contributes to disparities in infant mortality between the United States and other developed countries. https://www.selleckchem.com/products/azd1080.html We examined differences in the causes of term infant deaths across county poverty levels and urban-rural classification to understand underlying mechanisms through which these factors may act. We linked period birth/infant death files for 2012-2015 with US Census poverty estimates and county urban-rural classifications. We grouped the causes of term infant deaths as sudden unexpected death in infancy (SUDI), congenital malformations, perinatal conditions, and all other causes. We computed the distribution and relative risk of overall and cause-specific term infant mortality rates (term IMRs) per 1000 live births and 95% CIs for county-level factors. The increase in term IMR across county poverty and urban-rural classification was mostly driven by an increase in the rate of SUDI. The relative risk of term infant deaths as a result of SUDI was 1.6 (95% CI, 1.5-1.8) times higher in medium-poverty counties and 2.3 (95% CI, 1.2-2.5) times higher in high-poverty counties than in low-poverty counties. Cause-specific IMRs of congenital malformations, perinatal conditions, and death from other causes did not differ by county poverty level. We found similar trends across county urban-rural classification. Sudden infant death syndrome was the main cause of SUDI across both county poverty levels and urban-rural classifications, followed by unknown causes and accidental suffocation and strangulation in bed. Interventions aimed at reducing SUDI, particularly in high-poverty and rural areas, could have a major effect on reducing term IMR disparities between the United States and other developed countries. Interventions aimed at reducing SUDI, particularly in high-poverty and rural areas, could have a major effect on reducing term IMR disparities between the United States and other developed countries.